This section is intended to introduce the reader to aspects of art that may be related to various aspects of the present disclosure described herein, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure described herein. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Prior to natural gas being delivered to a customer from a high-pressure gas pipeline, its pressure is reduced through a throttling or pressure control valve to meet the distribution and utilization requirements. This throttling process of pressure reduction causes a lowering of the gas temperature as it approaches a constant enthalpy process. However, during the throttling process gas energy is spent without doing any work thereby resulting in lost or wasted energy. One method of power plants to capture this lost energy is by using a turbo-expander. In general, a turbo-expander, also referred to as turboexpander or a gas expansion turbine, is a centrifugal or axial flow turbine through which a high pressure is expanded to produce work, such as electrical energy. Since the generated work is extracted from the expanding high pressure gas, the expansion is approximated by an isentropic process (i.e., a constant entropy process) and the low-pressure exhaust gas from the turbine is at a very low near freezing or below freezing temperature, which can depend on the operating pressure and gas properties. However, the use of a turbo-expander in conventional power plants is currently very limited for capturing the energy/work generated from the pressure drop. In addition, the cooling effect of the temperature drop of the gas through the turbo-expander is further ignored, lost, and wasted, thereby leading to very in-efficient power plant systems.
Hence, what is needed is a system for not only recovering the energy and work from the pressure drop of the gas through a turbo-expander but to also recover and utilize the cooling effect of the temperature drop of the through the turbo-expander, thereby achieving an efficient power plant system with significant cost savings.